In all of the above varieties of lamps, the conductive lead-in wires which form part of the lamp's ignition structure are typically sealed within one end of the lamp's envelope using a press (or "pinch") sealing operation during which the glass comprising this end portion is heated and compressed by a pair of opposing, parallel-faced metallic press members which converge to engage the heated glass. At least one engagement per lamp is required and on some occasions, two or three are employed. Examples of such lamps are illustrated in U.S. Pat. Nos. 3,290,906 (Schilling et al), 3,752,636 (Warninck) and 3,884,615 (Sobieski). While such a technique has proven to successfully provide a hermetic seal of the metallic lead-in wires, the requirement of using a press seal possesses several drawbacks, particularly with regard to small volume lamps such as those of the subminiature type. Firstly, there exists a strong tendency for the two wires to "swim" within the molten glass during pressing, which in turn can result in the two becoming misaligned. This situation is understandably intolerable in subminiature photoflash lamps where precisioned, spaced-apart orientation is essential. Secondly, a press-sealed end adds appreciably to the overall length of the lamps envelope, a highly desirable feature serving to defeat miniaturization efforts. Thirdly, the necessity for using a press seal adds to the overall costs of producing the lamp in that such a technique understandably requires complex lamp manufacturing equipment, which itself is both costly to produce and operate.
It is believed therefore that a method of making an electrically-activated photoflash lamp which can be readily produced without the need for a press seal end portion while still possessing a sound, hermetically sealed envelope would constitute a significant advancement in the art.